The invention is directed to polyalkene-substituted carboxylic acid compositions having a reduced chlorine content, derivatives thereof useful as fuel and lubricating oil dispersants and dispersant/viscosity modifiers and methods for forming such compositions.
Compositions formed by reacting polyalkene-substituted carboxylic acylating agents with amines, alcohols and/or reactive metal compounds are known to be useful additives that provide fuel and lubricating oils with improved dispersing, detergent and/or viscometric properties. The polyalkene-substituted carboxylic acylating agents are themselves useful as emulsifiers. Such polyalkene-substituted carboxylic acylating agents are commonly formed by halogen-assisted reaction of a polyalkene and a carboxylic acylating agent. In a two-step process, as described for example, in U.S. Pat. No. 3,219,666, a polyalkene is chlorinated until there is, on average, at least one chloro group for each polyalkene molecule. Chlorination can be achieved by simply contacting the polyalkene with chlorine gas until the desired amount of chlorine is incorporated into the chlorinated polyalkene, usually at a temperature of about 75 to about 125xc2x0 C. In the second step of the two-step chlorination process, the chlorinated polyalkene is reacted with a molar equivalent, or a molar excess of an xcex1,xcex2-unsaturated carboxylic group, usually at a temperature of about 100 to about 200xc2x0 C. Alternatively, and as described for example by U.S. Pat. Nos. 3,215,707 and 3,231,587, a mixture of polyalkene and xcex1,xcex2-unsaturated carboxylic reactant can, in a single step process, be contacted with chlorine gas (e.g., by passing chlorine gas through the mixture with agitation) at an elevated temperature (e.g., 140xc2x0 C. or above).
Polyalkene-substituted xcex1,xcex2-unsaturated carboxylic acylating agents synthesized via chlorine induced condensation of polyalkenes and xcex1,xcex2-unsaturated carboxylic groups conventionally contain a residual chlorine content of 0.5 to 1%, which corresponds to 5,000 to 10,000 parts per million of chlorine. Thus, dispersants derived from polyalkene-substituted carboxylic acylating agents are a source of organochlorine in motor oils. Due to environmental concerns regarding the disposal of used motor oil, particularly in Europe, it has become desirable to eliminate or reduce the level of chlorine in motor oil additives and other industrial products. One way to address concerns regarding chlorine is to avoid the use of chlorine altogether by using a thermal process wherein a polyolefin and unsaturated dicarboxylic acid are heated together without halogen assistance, optionally in the presence of a catalyst (xe2x80x9cthermalxe2x80x9d or xe2x80x9cenexe2x80x9d reaction). Such a method is described, for example, in U.S. Pat. No. 3,361,673. However materials formed via the thermal route, in general, have a lower number of acylating groups per molecule. Another solution to the problem is to post-treat a chlorine-containing product to remove chlorine until the level of chlorine in the product is at an acceptable level. Certain methods for accomplishing this are known, particularly with polyalkene succinic dicarboxylic acid or anhydride (PIBSA) used as an intermediate in the manufacture of PIBSA/PAM (polyamine derivatives of PIBSA) dispersants. These methods, while capable of reducing chlorine content of PIBSA, can also adversely reduce the number of acylating groups, as expressed by a reduced saponification (SAP) number or level of active ingredient (AI). Also known are methods for obtaining dispersant intermediates by reacting highly functionalized polymer with acylating agents by maleation and chlorination of a polymer (e.g., polyalkene) backbone. However, these methods lead to the need for filtration due to high levels of tar. Processes that require filtration are less acceptable for both economic and environmental reasons.
U.S. Pat. No. 5,489,390 to Sivik et al. describes a process for reducing the chlorine content of an organochlorine compound in which the organochlorine compound is mixed with (a) an acid selected from mineral acids other than HI and HBr, and organic acids having a pKa of less than about 2; and (b) a source of iodine or bromine, for a period of time sufficient to reduce the chlorine content of the compound. Chlorine levels in the compound may be reduced by treatment with iodine and bromine compounds. However, as a result, both halogens are present in the final product. Further, as would be apparent to one of ordinary skill in the art, the post treatment of dicarboxylic systems with mineral acids can lead to decarboxylation as well as the degradation of the polymer.
U.S. Pat. No. 5,672,266 to Sivik et al. discusses a process for reducing chlorine content by post thermal treatment, as in U.S. Pat. No. 5,489,390, using a Lewis acid in the absence of organic carbon. The Lewis acid is selected from salts of zinc, magnesium, calcium, iron, copper, boron, aluminum, tin, titanium and mixtures thereof. The low-chlorine-content products formed by said process again contain halogen other than chlorine, such as bromine or iodine.
U.S. Pat. No. 5,885,944 to Pudelski et al. (and EP 0 808 852) describes a method of reducing chlorine content by post treatment with elemental sulfur of polyalkylene-substituted carboxylic acylating agents which contain chlorine remaining from the chlorine induced condensation of polyalkenes and xcex1,xcex2-unsaturated carboxylic acid moieties. The described method results in the formation of hydrogen sulfide as a by-product and a sulfur-containing PIBSA, which displays a high kinematic viscosity.
U.S. Pat. No. 6,077,909 to Pudelski et al. and EP 0 899 276 each describes a method for providing polyalkylene-substituted carboxylic acylating agents having a reduced chlorine content which relies on the use of, as the polyalkene reactant, a polyolefin having a total of tetra- and tri-substituted unsaturated end groups in an amount up to about 90 mole percent, wherein the polyolefin is reacted with halogen on a molar basis up to an amount equal to the moles of tetra- and tri-substituted end groups.
EP 0 684 262 describes a process for reducing the chlorine content of chlorinated polypropylene or polyisobutylene, or a mixture of polypropylene and polypropylene succinic anhydride or polyisobutylene and polyisobutylene and polyisobutylene succinic anhydride in which the polymer or polymer and succinic anhydride mixture is treated with heat for a specified period of time.
EP 0 665 242 describes a method for reducing the chlorine content of polyalkene substituted carboxylic acylating agents which involve treatment with a halogen other than chlorine (e.g., iodine or bromine).
U.S. Pat. No. 5,777,025 to Spencer et al. and EP 0 014 288 describe a method of reducing the amount of sediment that results from a thermal, or ene reaction of polyolefin and unsaturated dicarboxylic acid in which the reaction is conducted in the presence of a small amount of a strong organic acid, such as a hydrocarbyl-substituted sulfonic acid.
In accordance with one aspect of the present invention, there is provided a method of reducing the chlorine content of a polyolefin-substituted carboxylic acylating agent having a residual chlorine content in which the polyolefin-substituted carboxylic acylating agent is subjected to heat-soaking in the presence of an xcex1,xcex2-unsaturated acid or anhydride.
In accordance with another aspect of the present invention, there is provided a method of reducing the chlorine content of a polyolefin-substituted carboxylic acylating agent having a residual chlorine content in which the polyolefin-substituted carboxylic acylating agent is subjected to heat soaking in the presence of an xcex1,xcex2-unsaturated acid or anhydride and a sediment reducing agent.
In accordance with a third aspect of the invention, there is provided a method of further reducing the chlorine content of a product of a chlorine-assisted reaction of a polyolefin and xcex1,xcex2-unsaturated acid or anhydride reactant which involves mixing the reactants using mixer blade(s) having a specific configuration.
Polyolefin-substituted carboxylic acylating agents formed in accordance with the method of the present invention, in addition to a lower residual chlorine content, can simultaneously provide a higher saponification number with succination values up to about 2 and an increased level of active ingredient (A.I.) and sediment values that are reduced to levels at which filtration of the final product is not required.